Checks
| Actions
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DEFINITION:
Fuel ignites in the intake manifold, or in the exhaust system, making loud
popping noise.
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Preliminary Checks
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Sensor/System
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| • | Inspect for the following intermittent ignition system conditions: |
| - | Intermittent crankshaft position (CKP) Sync or CKP 18X signal |
| - | Intermittent ignition feed circuit or sensor ground circuit to
the crankshaft position sensor or the camshaft position (CMP) sensor. |
| - | Intermittent 3X reference signal |
| - | Intermittent camshaft position signal |
| • | Inspect the throttle body inlet screen for foreign objects or
damage that can affect the mass air flow (MAF) sensor airflow sample. |
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Fuel System
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Ignition System
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| • | Test for proper ignition voltage output using the following steps: |
| - | Clip the J 26792
Spark Tester to engine ground. |
| - | Connect one end of a spark plug wire to the spark tester, leave
the other end of the spark plug wire to the coil being tested. |
| - | Connect another spark plug wire between the remaining coil tower
on the coil being tested and ground. |
| - | Crank the engine while observing the spark tester, a spark should
be observed. |
| - | Repeat the above steps for each coil. |
| • | If adequate spark is not present at the coils, test for the following
conditions: |
| - | Coils--Evidence of carbon tracking or arcing, cracks in the
coils, or a resistance value outside the specified range: |
Coil Secondary Resistance
5000-8000 ohms (5K-8K ohms)
| | Important: Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent condition. Ignition components will arc to ground
when a secondary component is malfunctioning.
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| - | Spark plug wires--Inspect for the following conditions: |
| • | Evidence of cross firing |
| - | Spark plug wires--Inspect for a resistance value more than
the specified value: |
Spark Plug Wires Resistance
9840 ohms per meter (3000 ohms per ft) | - | Malfunctioning ignition control module (ICM). |
| - | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
| • | Remove spark plugs and inspect for the following conditions: |
| - | Burned or damaged electrodes |
| • | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
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Engine
Mechanical
| Test for the following:
| • | Sticking or leaking valves |
| • | Excessive oil in combustion chamber-Inspect for evidence
of leaking valve seals |
| • | Low cylinder compression |
| • | For incorrect engine parts, inspect the following basic parts: |
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Additional Tests
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| • | Inspect the intake and exhaust manifolds for casting flash. |
| • | Inspect the exhaust system for a possible restriction in the following
components: |
| - | Damaged or collapsed pipes |
| - | Heat distress or possible internal failure in the muffler |
| - | Plugged three-way catalytic converter--Test for possible
plugged conditions. Refer to
Restricted Exhaust
in Engine Exhaust. |
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